Soot may be formed in an engine where fuel is directly injected to cylinders of the engine. Specifically, soot may form when fuel is injected to an engine cylinder while the engine is operating at higher speeds and loads. The soot may form from incomplete combustion of hydrocarbons since there is less time available to atomize fuel injected to the cylinder at higher engine speeds. Soot formation may also be influenced by introducing hydrocarbons to the cylinder via purging fuel vapors stored in a fuel vapor storage canister. In particular, since the purged fuel vapors may be combined with air entering the engine before the air enters the cylinder, it may be more difficult for fuel injected to the cylinder to vaporize and combine with the air-fuel mixture entering the cylinder. Consequently, an amount of soot produced by an engine may increase when stored fuel vapors are purged to the engine.
The inventor herein has recognized the above-mentioned limitations and has developed a method for operating an engine, comprising: supplying an amount of fuel from a fuel vapor storage canister to a cylinder; and adjusting a number of fuel pulses supplied to the cylinder via a fuel injector during a cycle of the cylinder in response to the amount of fuel supplied to the cylinder during the cylinder cycle from the fuel vapor storage canister.
By supplying fuel to a cylinder in a number of fuel pulses while fuel is also supplied to the cylinder via a fuel vapor storage canister, it may be possible to reduce soot formation in the combusted products of the cylinder. In particular, soot formation of a cylinder may be reduced by performing multiple injections of fuel during a cylinder cycle. In one example, a number of fuel pulses supplied to a cylinder during a cylinder cycle may be maximized to promote fuel vaporization even though a mixture of air and fuel enters the cylinder via an intake valve of the cylinder.
The present description may provide several advantages. In particular, the approach may provide reduced soot formation in combustion byproducts. In addition, the method may reduce engine system cost by reducing the possibility of having to provide a particulate trap for the engine. Further, if the engine system includes a particulate filter, the particulate filter may need to be regenerated less frequently when the approach is applied.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.